After the Orlando shooting, Rubio said he was reconsidering the decision, telling reporters the terror attack had prompted him to rethink his "service to country."

Florida Sen. Marco Rubio speaks to the media. Joe Raedle/Getty Images

In his statement Wednesday, Rubio acknowledged that he has "often said that the US Senate can be a frustrating place," but argued that "no matter who is elected president, there is reason to worry" and the Senate could play a key part.

"[A]s we begin the next chapter in the history of our nation, there's another role for the Senate that could end up being its most important in the years to come: The Constitutional power to act as a check and balance on the excesses of a president," Rubio said.

The conservative firebrand said, however, that "in the end" his decision was made "back home in West Miami over Father's Day weekend" with his family.

"There were two paths before us. There was one path that was more personally comfortable and probably smarter politically," Rubio said. "But after much thought and prayer, together we chose to continue with public service; to continue down the path that provides the opportunity to make a positive difference at this critical and uncertain time for our nation."

"In the end, there was simply too much at stake for any other choice."